Echocardiograms were obtained before and six months after surgical closure of an atrial septal defect in nine patients. Preoperatively, all patients had right ventricular dilatation, and 8 (89%) had abnormal ventricular septal motion. Postoperatively, no patient had a residual shunt, but right ventricular dilatation and abnormal septal motion persisted in 6 (67%). In both groups, the magnitude and direction of septal motion was predicted by the intracardiac position of the septum at end-diastole.